There are many environmental exposures that are important. Describe for each of

Question

There are many environmental exposures that are important. Describe for each of “three groups” in the general population why that group has increased susceptibility to environmental toxicants. Include in your response whether you are referring to those that are at a greater risk of being exposed OR those where once the exposure occurs, the effects are greater.

Group 1: Children less than 2 years of age

Group 2: Individuals who have poor lung function.

Group 3: Individuals in poor housing in close proximity to agriculture or industry

Explanation / Answer

Group 1: Children less than 2 years of age

The differing susceptibility of children to harm from environmental exposures results from their development—a dynamic process with many physiologic, metabolic, and behavioral aspects. Children are at increased risk because of their increased exposures and increased vulnerability.

These needs result in a greater exposure per kilogram to toxicants. Increased exposures also arise from children's normal development, such as the hand-mouth and hand-object behavior exhibited by toddlers. Increased vulnerability results from children's rapidly growing and developing organ systems, such as the central nervous system and lung which, compared with adults are especially susceptible to toxic insults.

Exposure to the same chemical may cause different health outcomes in children compared with adults. A well-known example is the effect of lead on young children's developing nervous systems. Lead does have effects on the nervous systems of adult workers, which result in peripheral neuropathies. For children, however, intellectual development is exquisitely sensitive to even small amounts of lead; this sensitivity is not seen in adults.

Group 2 : Individuals who have poor lung function

With an ever increasing number of elderly individuals in the world, a better understanding of the issues associated with aging and the environment is needed. The respiratory system is one of the primary interfaces between the body and the external environment. An expanding number of studies suggest that the aging pulmonary system (>65 years) is at increased risk for adverse health effects from environmental insult, such as by air pollutants, infection, and climate change. However, the mechanism(s) for increased susceptibility in this subpopulation is not well understood. In this review, we provide a limited, but comprehensive overview of how the lung ages, examples of environmental exposures associated with injury to the aging lung and potential mechanisms underlining the increased vulnerability of the aging lung to injury from environmental factors.

Group 3 : Individuals in poor housing in close proximity to agriculture or industry

We identified studies of environmental proximity analyses in relation to health through the National Library of Medicine's PubMed, using search terms that combined proximity to and adverse pregnancy outcomes (birth defects, fetal death, low birth weight, preterm birth, and spontaneous abortion), childhood cancer, cardiovascular and respiratory illnesses, end-stage renal disease, and diabetes. We also identified additional relevant studies in these studies’ bibliographies. With respect to cancer, we focused our review primarily on childhood cancers. Given the relatively long induction and latent period of solid tumors in adults, studies would need to include residential histories for as many as 15 to 30 years before a cancer diagnosis to capture pertinent environmental exposures. Although several recently published studies have included extensive residential histories,2–4 such studies are scarce. Even though various respiratory and cardiovascular conditions may originate many years before manifestation of overt disease, environmental exposures to pollutants could have acute effects, for example, precipitating asthma attacks or myocardial infarction in susceptible individuals.

We summarized information from each study regarding target populations, type of study design used, health outcomes included, methods of proximity analyses and exposure assessment, major findings, and limitations. We also examined study results for evidence of racial or economic disparities in health outcomes in relation to residential proximity. In addition to discussing overall findings, we summarized the conclusions of studies that had minimal limitations with respect to exposure assessment and outcome.

A wide variety of methods were used in the reviewed studies to examine the relation between proximity to potential environmental hazards and adverse health outcomes, including spatial coincidence analyses (e.g., residence in a zip code with 1 hazardous waste sites), distance-based analyses (e.g., residence 1 mile of industrial facilities as defined by a 1-mile buffer), and pollution plume modeling (i.e., the dispersion footprint of the pollutant as a proxy for exposure). The most frequently used method was distance-based analysis.

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